It is well known in the art that axle assemblies include elements such as wheels, gears and the like which are rotatably connected to a spindle or axle. Devices of the above mentioned character have been found to be useful on land vehicles in general and specifically on mobile child carriers thereby imparting mobility to such child carriers. As used herein, mobile child carriers include but are not limited to strollers, prams, mobile entertainers, and the like. Typically, mobile child carriers are provided with wheels which include centrally disposed throughbores. Such mobile child carriers often include a frame having at least one axle attached thereto. The axles are sized to be passed through the throughbores such that the wheels are rotatably coupled to the axles. Although such devices operate effectively, such devices have presented several drawbacks as well. Specifically, the wheels may slide axially along the axle until becoming disengaged therefrom.
A variety of devices have been suggested to retain wheels in association with axles while also not unduly inhibiting the rotatability of the wheels. One known device is the wheel axle retention mechanism currently employed on several strollers marketed by Graco Children's Products such as the stroller marketed under the trademark LITERIDER.TM.. As shown in FIG. 9, LiteRider strollers teach an axle 100 which includes an outer end 102 having a beveled edge 104 and an annular groove 106 formed in the axle 100 and spaced a distance from the outer end 102. In addition, LITERIDER.TM. strollers include a retainer 108 to rotatably couple a wheel, not shown, on the axle 100. The retainer 108 includes an annular ring portion 110. Extending from the annular ring portion 110 is a skirt portion 112. Specifically, the skirt portion 112 is discontinuous and includes a plurality of legs 114. Further, the retainer 108 includes an engagement portion 116 which has a finger 118 attached to each leg of the plurality of legs 114. Each finger 118 extends inwardly within groove 106 such that forces directed upon the retainer 108 by the wheel along the axial direction of the axle 100 are thereby resisted.
Although devices of the above mentioned character operate effectively to retain a wheel in rotatable association with an axle, such devices could also be substantially improved upon. For instance, it has been found that such retainers often rotate along with the wheel as it rotates about the shaft due to frictional forces exerted upon the retainer by the wheel. As the retainer rotates, friction is in turn created between the axle and the retainer. Commonly, the groove of such axles are formed from a metal material while the retainer is commonly formed from a plastic material. It has been found that such an arrangement often leads to premature part failure since the axle carves into or wears against the retainer. Specifically, it has been found that the groove of such axles often includes sharp edges which carve into and wears against the portion of the retainer adjacent the groove.
Various other devices have been suggested to interconnect a wheel to an axle while minimizing part degradation. One such device is disclosed in U.S. Pat. No. 5,188,430 to Chiu. Chiu suggests a structure for golf car wheels including a wheel having a pair of hole bushings mounted within the wheel. The hole bushings are in turn pivotably coupled to a shaft bushing fitted through the wheel and contacting the wheel bushings. The structure to Chiu also includes a shaft having two recesses 42 which are received within the wheel bushing. Such devices operate by allowing the wheel bushing to rotate relative to the hole bushings. To minimize part wear between the shaft and the wheel bushing, the shaft is fixed relative to the wheel bushing by two elastic clamping fingers disposed on the wheel bushing which engage the two recesses on the axle. Accordingly, the axle is fixed relative to the wheel bushing such that the frictional forces which occur due to the rotation of the wheel are concentrated between the wheel bushing and the hole bushings.
Although the above mentioned device provides advantages, such devices also have several drawbacks as well. Specifically, such devices do not operate to reduce friction between a retainer and an axle. Instead, such devices merely operate to fix an axle relative to a bushing. Further, the two clamping fingers are attached to two pressing ends; however, the axle and wheel bushings are engaged at only two locations. Although such devices reduce frictional wear, the stresses realized by fixing the wheel bushing relative to the axle is concentrated at the two locations where the clamping fingers engage the recesses of the axle. Accordingly, the stresses realized between the wheel bushing and the axle may result part failure due to the discontinuous stress concentrations.
As can be best appreciated by one skilled in the art, several advancements in the art would be desirable. Specifically, it would be desirable to have a retention mechanism that may secure a wheel to an axle thereby preventing the wheel from becoming undesirably disengaged from the axle. It would also be desirable to have a device which is designed to prevent friction induced rotation between the wheel and the axle thereby minimizing wear and premature part failure of the retention mechanism. In addition, it would also be desirable to have a retention mechanism that distributes the stresses realized within the retention mechanism caused by rotation of the wheel once again minimizing part failure.